“And transportation experts warn that plenty of worthy projects would likely fall by the wayside if P3s were the only option. “We’re not going to have private companies filling our potholes or expanding our bus system, because those things aren’t profitable,” says Carl Davis, research director at the D.C.-based Institute on Taxation and Economic Policy. For example, if tax credits become the main source of federal dollars, it could doom projects like the build-out of the Second Avenue subway or the Gateway rail tunnel under the Hudson, neither of which could be easily monetized.”